Medical imaging technology is a diagnosis technique of visually representing muscles, tendons, and many internal organs, to capture their size, structure, and pathologic lesions with real-time tomographic images, based on an ultrasound or photoacoustic means. Medical imaging is also used to visualize fetuses during a periodic checkup or in an emergency situation. Ultrasound has been used to image the interior of the human body for at least 50 years and has become one of the most widely used diagnostic tools in modern medicine. The ultrasound technique is low in cost and easy in mobility, relative to magnetic resonance imaging (MRI) or X-ray computed tomography (CT).
The principle of ultrasound imaging is as follows. First, an ultrasound image is made by bringing a measurement object into contact with a probe and receiving ultrasound reflected by generation of ultrasound waves. If ultrasound is generated, an ultrasound wave passes into a medium within a very short time and the ultrasound wave is reflected upon passing between two media having different acoustic impedances. In the ultrasound imaging technique, such a reflection wave is measured and a distance is calculated based on the time until reflection sound returns back, thereby achieving imaging.
In such ultrasound imaging, an echo signal returning from a target object attenuates according to depth and thus bandwidth of the signal varies. To improve a signal-to-noise ratio (SNR) caused by variation in bandwidth, a signal processing procedure is needed. An overview of ultrasound signal processing is given in the prior art document proposed below.